This invention is directed to molding compositions comprising flame retardant ternary blends of a polyetherimide, a polyphenylene ether and block copolymer of a vinyl aromatic compound and alkene compound of the A-B-A type.
Polyetherimide resins are well known in the art and are of considerable commercial value for use in molding compositions because of their excellent physical, chemical and thermal properties. The high glass transition and heat deflection temperatures exhibited by these polymers permit their use in high performance applications previously reserved for metals and some thermoset resins. While polyetherimides are generally known to have high glass transition temperatures, for many applications, it would be desirable to have a resin with a lower cost, yet which maintains the high glass transition temperatures and other advantageous physical properties of polyetherimides.
It is known that the cost of polyetherimides can be lowered by forming blends of those polymers with a polyphenylene ether polymer. See, White et al., U.S. Pat. 4,431,779. Although such blends maintain many of the physical properties of polyetherimides, it is desirable to have a polymer product with improved Izod impact values.
Binary blends of polyetherimides and block copolymers of a vinyl aromatic hydrocarbons and a diene hydrocarbon have been prepared for the primary purpose of improving the impact properties of the polyetherimide polyestercarbonates. See, Giles et al., U.S. Pat. No. 4,587,299. Again, although these blends exhibit certain advantageous properties, they have not been found to possess the desired low cost needed for a number of applications.
Thus, there exists a need for a polymer blend which exhibits low cost, high Izod impact values and improved flexibility than polyetherimides.